The proposed studies stem from our previous research on the antifungal activity of dicationic molecules. These initial in vitro studies on over 300 dication molecules showed that leading compounds were both inhibitory and fungicidal against Candida albicans and Cryptococcus neoformans with MIC80S of <0.09 g/mg and MFCs of 0.10 g/ml against both organisms. Our studies also demonstrated that the compounds were active against Aspergillus fumigatus, Fusarium solani, Candida species other than C. albicans and fluconazole-resistant strains of C. albicans and C. neoformans. An outside laboratory confirmed our in vitro data and also showed that leading compounds against A. fumigatus had IC50 values that were less than 0.0050 mu g/ml and selectivity indices, when compared to HeLa cell, over 2000. More importantly, the outside laboratory demonstrated that one of the compounds was equally as active as fluconazole in a mouse survival model of candidiasis. The above findings along with our studies on the toxicology and pharmacology of dicationic compounds clearly show that these molecules have great potential as antifungal agents. The current proposal will expand these initial studies by synthesizing over 2,400 related molecules per year utilizing combinatorial chemistry technology and testing these molecules in an in vitro model for activity against C. albicans and A. fumigatus and toxcity in THP-1 cell (human monocytes). Since the exact mechanism of antifungal activity is not known, and previous results indicated that more than one mode of action may contribute to their antifungal activity the compounds will be screened against the organism rather than a specific target. The antifungal data will be subjected to detailed QSAR and modeling studies and these results will be used to guide either the expansion of proposed libraries, the development of new libraries, or off resin synthesis of a small subset of related molecules. Finally, selected molecules will be tested in animal models of fungal infections. This proposal brings together a seasoned group of investigators with over seven years of successful collaboration on antimicrobial research. Utilizing the combinatorial chemistry methodology to build focused libraries coupled with high-throughput screening and data management will optimize the groups chances of achieving the goal of this project; the discovery of new antifungal agents.